This invention relates to a jamb-like frame commonly referred to in the art as a doorjamb employed to provide a suitable seal surface and support for a coke oven door that forms a removable closure at the end of a coke oven chamber, and more particularly the present invention relates to such a doorjamb embodying a construction to provide the necessary stiffness to withstand a considerable bending moment without undue deflection arising out of the forces developed to support a coke oven door thereon as well as a construction to inhibit warping and distortion due to the high temperature environment to which the jamb is subjected when mounted for operation next to the refractory brickwork for a coke oven chamber.
In a battery of modern-day coke ovens, a frame conventionally identified as a doorjamb is mounted next to the refractory brickwork forming the coke oven chambers. A doorjamb is mounted in this manner at each end of every coke oven chamber in the coke oven battery for removably supporting a coke oven door. Because of the height of these chambers, usually about 14 feet, large forces are required to support and maintain a sealed relation with a coke oven door under particularly adverse conditions because of the highly-heated environment. A portion of the doorjamb is seated against the refractory of the coke oven chamber and the seated portion experiences the same temperature excursions as the refractory brickwork of the coke oven battery during the coking operation. Moreover, the doorjamb undergoes rapid quenching when, for example, a door fire is extinguished with water. A conventional doorjamb has a rather natural tendency to bow along its vertical height when the jamb is initially put into use on a coke oven chamber since the part of the doorjamb touching the refractory undergoes heating to a much higher temperature than the remaining part of the doorjamb. The temperature differential between the outer and inner regions of the jamb creates a concave bow or a bent-shape to the jamb. This thermally-responsive condition is essentially reversible since, in most instances, when the jamb is removed from the refractory brickwork, the thermally-responsive forces creating the distortion are dissipated and the frame resorts to its original shape. As a general proposition, the amount of a thermally-induced bow to a doorjamb varies with the mean slope of the temperature distribution across the jamb in cross section. The temperature distribution varies with the depth to which the jamb penetrates into the slot-like opening in the refractory brick of the furnace as well as the material used to form the jamb. Because most doorjambs have a T-shaped cross section, a temperature gradient exists across the head of the jamb which is in contact with the refractory brickwork and a different temperature gradient exists across the central section to the T-shaped configuration because the projected section is located outwardly of the refractory brickwork. A temperature gradient of 40.degree. is typical across the head section of the jamb which is in contact with the refractory brickwork. This temperature gradient contributes to the well-known deflecting phenomenon known as hourglassing. The temperature gradient across the web section between the head and the free end thereof is typically on the order of 150.degree. F. causing a bow-like warping to the jamb in the direction of its vertically-extended height. It is to be understood, of course, that the temperature gradients discussed above are greatly exceeded under extreme service conditions. Normally, if a linear temperature distribution exists across both the head section and the web section to the T-shaped configuration of a doorjamb, no stresses in the vertical side rails result from the bowing of an unrestrained jamb. Assuming a constant coefficient of thermal expansion, the amount of expansion at each temperature level is proportional to the temperature. However, if there is a substantial variation from a straight-line temperature distribution, then stresses will be induced which can be of substantial magnitude. Non-linear temperature distribution across the cross-sectional shape of a doorjamb occurs from transient heating effects, for example, due to a sudden heating of a portion of a jamb or from a steady-state condition involving irregular geometry to the cross-sectional shape of the jamb. Generally, a non-linear temperature distribution along a given cross section of a doorjamb causes stresses in the longitudinal direction of the side rails or vertical sides of the jamb. Design criteria for a doorjamb demand consideration of the development of stresses which result in short or long-term yielding of the jamb material. Even low thermal stresses will cause yielding, especially over a long period of time. Stresses due to an externally-applied load on highly-heated material result in yielding of the jamb material.
The thermal conditions adversely affecting a doorjamb cause both bowing and hourglass warpage conditions. Simple jamb bows of up to 3/4 inch are commonly encountered on newly-installed jambs that are 14 feet in height. This bowing occurs as a curvature to the jamb into or out of the vertical plane of the oven due to the thermal or mechanical forces. Usually, however, bowing is due to a temperature differential across the cross section of the jamb. The usual door seal strip cannot mate with a jamb surface to provide adequate sealing when the jamb has a large bow or varying curvature.
Moreover, hourglassing which is a tendency for the long sides of the jamb to deflect toward each other due to the temperature differential impedes the placement of a coke oven door because of interference with the deflected portion of the doorjamb. The jamb seal surface will not align with the door seal strip. Both of these warped conditions of a doorjamb can bring about the unacceptable emissions of smoke and coke oven gas into the atmosphere.